The Australian five ounces gold piece (abbreviated as 5 oz and designated with Au for "gold") is a bullion coin format. Uniquely, in Australia there are two mints independently authorised to strike legal tender: the Royal Australian Mint (which also makes the country's circulating coinage) and the Perth Mint which only makes collector and bullion coins, as well as other bullion products.
The Australian Koala series by the Perth Mint is issued in many bullion formats, including the large five ounces of gold size.
The reverse design changes every year, always featuring a koala - one of the most famous and distinctive animals native to Australia. The gold five-ounce coins have a face value of 500 dollars, but this is only symbolic - as the bullion value of their precious metal content is much higher. The overall weight is slightly more than five ounces, so that the pure gold content is exactly 5.000 AGW (troy ounce Absolute Gold Weight).
The Mint says about the coin:
"The unique charm of Australia’s sleepy and placid koala is beautifully illuminated on this prestigious gold coin that is crafted with assiduous attention to detail to meet the expectations of our most fastidious collectors. This Australian Koala coin is struck from 5oz of 99.99% pure gold to the highest proof specification with a mirror-like polished background and elegantly frosted design elements." | 
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